For cartridges adapted to be filled with printing material, for example, cartridges for supplying ink, which is one example of a printing material, to an inkjet printer, are known. With this kind of cartridge, in the past, items were known which had a case having a recess which is filled with ink, a sheet member for sealing the case recess, and a supply port for supplying the ink filled inside the recess to the inkjet printer. See, for example, Unexamined Patent Publication No. 2011-140189 and U.S. Patent Application Publication No. 2012/133713.